1. Field of the Invention
The present invention relates to an image processing method, and particularly to an image processing method which intentionally changes image tone of an image represented by image data.
2. Description of the Related Art
There has conventionally been known an image processing system in which an image exposed and recorded on a photographic film is read by a film reading device equipped with a reading sensor such as a CCD sensor, image processing including various correction is effected for image data obtained by reading the image, and based on image data subjected to the image processing, the image is recorded on a recording material. This image processing system has a merit over a conventional photographic processing system in which a film image is recorded on a photographic printing paper by plain (analogue) exposure, in that the quality of a recorded image can be freely controlled by image processing for image data.
As a filter mounted to a camera when an image is exposed and recorded on a photographic film, there have been known various filters such as a color-temperature conversion filter, a color correction filter, an ND filter, and a deflection filter. In addition to the above-described filters, a special filter for intentionally changing image tone (for example, a cross filter for making one or more striations, whose center is a high-luminance region in a image, on the image in a radial manner when a sparkling surface of water or night scene is photographed) is also provided.
However, the special filter such as a cross filter is used to intentionally change image tone as described above, and therefore, it is not always used at the time of photographing. Only when photographing of a scene with image tone changed is required, the special filter is mounted in a camera by a photographer, and after photographing of the scene has been completed, the special filter is removed from the camera and is stored. Accordingly, when an image of which tone is changed is obtained, there was a problem in that handling of a special filter, which includes the need of giving attention to storage of an unused special filter, is complicated.
Further, almost all of relatively low-cost cameras such as lens-attached films and compact cameras or digital cameras which have rapidly spread in recent years does not allow mounting of filters therein. When photographing is effected using these cameras, it is not possible to obtain an image of which tone is intentionally changed using a special filter such as a cross filter.
Moreover, when a camera in which the special filter can be mounted is used, an image of which image tone is changed can be obtained only by using the special filter at the time of photographing. However, it was not possible to change the image tone of the image photographed without using the special filter after photographing, for example, observing a finished state of an image photographed without using the special filter.
The present invention has been devised in view of the above-described facts and an object thereof is to provide an image processing method in which an image equivalent to that of which tone is intentionally changed using a special filter can be easily obtained without using the special filter.
In order to achieve the above-described object, an image processing method according to a first aspect of the present invention comprises the steps of extracting a bright region in an image based on image data and, based on the extracted bright region, synthesizing striation data, which represents striations extending from the bright region, with the image data.
In the first aspect of the present invention, a bright region in an image is extracted based on image data. The above-described image data may be image data obtained by reading a film image exposed and recorded on a photographic film using an ordinary camera or an image recorded on other recording medium such as plain paper, or may be image data stored in an information storage medium by a digital camera, or may be image data which represents density or luminance. Further, according to a second aspect of the present invention, extraction of the bright region in the image can be effected by extracting highlight points in the image based on the image data and extracting a region in which highlight points concentrate.
Then, in the first aspect of the present invention, based on the extracted bright region, striation data which indicates striations extending from the bright region is synthesized with the image data. According to a third aspect of the present invention, first striation data which indicates a plurality of striations extending from the bright region in a radial manner can be used as the striation data. Further, according to the third aspect of the present invention, second striation data which indicates a striation extending from the bright region and including polygonal high-luminance regions may also be used as the striation data.
As a result, an image represented by the image data becomes an image in which striations extend from the bright region, and therefore, a tone of the image represented by the image data can be changed to that similar to an image obtained by photographing using a cross filter or the like. As described above, an image having a peculiar tone which can be obtained only by photographing using a special filter such as a cross filter whose handing has been conventionally complicated can be obtained without photographing using the cross filter or the like. For this reason, according to the first aspect of the present invention, an image similar to that whose tone is intentionally changed using a special filter such as a cross filter can be easily obtained without using the special filter such as a cross filter.
Meanwhile, the striation data to be synthesized with the image data may be generated based on the extracted bright region, for example, when the striation data is synthesized with the image data. Alternatively, when with plural kinds of striation data being in advance generated, striation data is synthesized with the image data, striation data to be synthesized may be selected from the plural kinds of striation data based on the extracted bright region.
Further, the length, width, color tint, and the like of striations appearing on a photographed image by photographing using a special filter such as a cross filter each vary in accordance with a characteristic amount of a light source (i.e., a striation generating source corresponding to the bright region on the image). For this reason, a fourth aspect of the present invention is characterized in that, in the first aspect of the present invention, parameters which define a striation to be synthesized are determined based on characteristic amounts of at least one of the brightness, size, and color tint of the extracted bright region, and the striation data is generated or selected based on the determined parameters.
In the fourth aspect of the present invention, as the parameter which defines striations, the length, width, color tint, and the like of striations are used. For example, as the brightness (luminance) of the bright region becomes high (or as the size of the bright region becomes large), the length of a striation can be increased or the width of a striation can be made larger. Further, the color tint of the striations can be determined so that, for example, the color tint of the striations coincides with the color tint of the bright region.
According to the fourth aspect of the present invention, the parameter which defines striations is determined based on at least one of characteristic amounts of brightness, size, and color tint of the bright region, and based on the determined parameter, the striation data is generated or selected. For these reasons, the striation represented by the striation data can be approximated to that appearing on a photographed image when photographing is effected using a special filter such as a cross filter. Accordingly, unnaturalness caused by the striation applied to an image during visual observation of an image can be removed by synthesizing the striation data with the image data.
Further, since there are various kinds of special filters such as a cross filter, there are also obtained various kinds of striations applied to a photographed image by a cross filter. For example, the shape of a striation appearing on a photographed image may be set in such a manner that the width of the striation is gradually made small or varies periodically as the distance from the high-luminance region increases. Further, a striation whose hue periodically varies may also be generated.
For this reason, according to a fifth aspect of the present invention, it is preferable that striation data be generated so that at least one of width and color tint of a striation varies in accordance with a distance from a bright region. In the fifth aspect of the present invention, at least one of the width and color tint of the striation is varied in accordance with the distance from the bright region, and therefore, various kinds of striations applied to a photographed image can be reproduced using various special filters.
Further, in the present invention, there is a possibility that an unnatural image be obtained if striations are applied to all of bright regions extracted from the image. For example, when a light emitter such as a fluorescent lamp, which emits homogeneous light from a relatively large area exists as a subject in an image, if striations are applied to the light emitter by extracting the light emitter as the bright region, an unnatural image is obtained. For this reason, a sixth aspect of the present invention is characterized in that, in the first aspect of the present invention, based on the shape of each the extracted bright regions, a bright region to which a striation is applied by the striation data is selected from the extracted bright regions.
In the sixth aspect of the present invention, a bright region to which striations are applied is selected based on the shape of the bright region, and therefore, by, for example, applying striations only to bright regions whose shape are circular or substantially circular, a bright region corresponding to a light emitter such as a fluorescent light, which is unnatural due to striations applied thereto, can be excluded from the bright regions to which striations are applied. Accordingly, striations can be applied to an image represented by image data without causing unnaturalness.
On the other hand, in the present invention, the image data with striation data synthesized can be used for recording an image on a recording material or can be stored in an information storage medium. In this case, as described in a seventh aspect of the present invention, prior to recording of an image on a recording material or storage in the information storage medium, an image represented by the image data (image data prior to the striation data being synthesized) or image data with the striation data synthesized is displayed on display means. Meanwhile, when the image represented by image data with the striation data synthesized is required to be displayed on the display means, prior to recording of an image on a recording material or storage in the information storage medium, the image with the striations applied thereto can be confirmed visually in advance, which is preferable.
Further, in the seventh aspect of the present invention, a bright region to which striations are applied by striation data is selected in accordance with an instruction inputted based on an image displayed on the display means and the striation data is generated, or selected, or corrected so as to be synthesized with the image data. Meanwhile, the instruction inputted based on the image displayed on the display means may be an instruction for applying striations to all of bright regions existing in a specified range of an image or may be an instruction for applying no striation to all or one of bright regions existing in the specified range. Due to generation, or selection, or correction of striation data in accordance with the above-described instruction, striations can be applied to an arbitrary one of the extracted bright regions and an image in which striations are applied to a desired bright region can be obtained.
Further, when the image data with the striation data synthesized is used for recording an image on a recording material, it is necessary to execute gradation conversion which converts a density range of an image represented by image data in accordance with a range reproduced as an image on a recording material, and there is a possibility that a value of data of a high-luminance region in an image (i.e., a region in which a density is the minimum value or near the minimum value) may be saturated accompanied with the gradation conversion. In this case, an image represented by image data after gradation conversion becomes an image in which the high-luminance region is a white point. For this reason, information relating to color tint of the bright region is lost, and when the striation data is synthesized with image data subjected to gradation conversion, striations represented by the synthesized striation data may be seen unnaturally as compared with an image represented by the image data subjected to gradation conversion.
For this reason, an eighth aspect of the present invention is characterized in that, in the first aspect of the present invention, after the striation data is synthesized with the image data, the image data with the striation data synthesized is subjected to gradation conversion used for recording an image on a recording material. According to the eighth aspect of the present invention, the gradation conversion is performed after the striation data is synthesized with the image data, and therefore, the gradation conversion is performed simultaneously under the same condition for gradation conversion also for the striation data with the image data synthesized. Accordingly, the striation represented by the striation data can be prevented from being seen unnaturally.
Further, according to the fourth aspect of the present invention, even when the parameter which defines striations is determined based on characteristic amounts such as color tint of the bright region, any image data prior to gradation conversion includes, as information, characteristic amounts such as color tint of the bright region, and therefore, the characteristic amounts of the bright region can be accurately extracted by extracting the characteristic amounts of the bright region using the image data prior to gradation conversion.